Silencer for pneumatic devices



Sept. 25, 1956 J. JEFFoRDs SILENCER FOR PNEUMATIC DEVICES 4F'ilfed Jan. 23, 1955 INVENTOR NN m; om

JOSEPH JEFFORDS ATTORNEY United States Patent O SILENCER FOR PNEUMATIC DEVICES y Joseph Jeffords, Baltimore, Md.

Application January 23, 1953, Serial No. 332,892

12 Claims. (Cl. 181-50) This invention relates to silencers for pneumatic actuated devices, to structures for such silencers, to materials for such structures, and to their utilization.

A variety of structures have been used in the prior art for silencers of various types as for example in connection with pneumatic tools. They have not been very satisfactory. The use of some structures build up backpressure to such an extent as to interfere seriously with the tool operation. In other cases, the pneumatic staccato sound effect is not muilled or silenced suiciently.

Among the objects of the present invention is a silencer effectively useful for all kinds of pneumatic actuated devices to silence or mufe the sound thereof.

Other objects include materials particularly useful in such silencers.

Still further objects and advantages of the present invention will appear from the more detailed disclosure set forth below, it being understood that such more detailed description is given by way of illustration and explanation only, and not by way of limitation, since various changes therein may be made by those skilled in the art without departing from the scope and spirit of the present invention.

In connection with that more detailed disclosure, the drawing illustrates a structure in accordance with the present invention wherein:

Figure 1 is a vertical longitudinal section through the silencer structure;

Figure 2 is a tranverse section through the structure of Figure 1, on line 2-2 thereof;

Figure 3 is a perspective view of sound absorbing material desirably used; and

Figures 4 to 7 'are cross-sections through the sound absorbing material showing the stages used in its production.

In accordance with the present invention, a silencer is produced which is utilizable in connection with all forms of devices, tools, etc., operated by fluid such as air under pressure. It is particularly useful in reducing or eliminating the noise or sound caused by the exhaust from pneumatically powered tools, such as drills, chisels, hammers, riveters, chip hammers, etc. Such silencer may be used in any site where such devices are operated, but is particularly effective in areas adjacent residences, schools, churches, hospitals, etc. where reduction in noise is of fundamental importance not only to residents, pupils, patients, etc., but also in avoiding deafness to workers using such devices.

Silencers inaccordance with the present invention include a plurality of expansion chambers successively connected with a sound absorbing structure in each of the expansion chambers. The sound absorbing structure is desirably of special type and consists of non-metallic material containing a number of cells of substantial size, the cells being open to the expansion chamber. For most effective results, a number of the cells, and preferably each of them, is provided with a non-metallic ball placed in the cell and freely movable therein without escape ICC from the cell. For this purpose the cell opening to the expansion chamber is smaller in diameter than the ball so that the latter will be retained within the cell.

Means are provided to conduct the pneumatic operating fluid, such as air, through the silencer. For this purpose, an inlet connected to the exhaust of the tool carries the fluid into the first of the expansion chambers, the fluid then passing through the successive remaining chambers until an outlet from the last expansion chamber permits the fluid to be exhausted into the atmosphere at increased volume and reduced energy devoid of any substantial disturbing influence. The length of silencer structure and number of expansion chambers depends on the type and size of device with which it is used, theL pneumatic pressure that must be dissipated etc. There may be one or more of such expansion chambers, three frequently being desirable as illustrated. The cross-section of the final exhaust should not be less than that of the initial inlet to the silencer and proportions should be maintained throughout to give most effective silencer action. The inner walls of the expansion chambers are desirably lined with sound absorbing material particularly of the character described below; although other types of material may be used but less effectively. Specifically in the preferred form, use is made of the freely moving non-metallic balls as described herein, for dissipation of the energy of the pneumatic fluids in pneumatic actuated devices. The silencers of the present invention may be constructed as units adapted to be attached to the exhaust of penumatic actuated tools already on the market or may be built into such tools or devices as part of their unitary structure.

Considering more particularly the illustrative device shown in the drawing a sleeve 1 desirably of metallic material provides a continuous internal bore divided into successively connected, lineally-disposed expansion chambers 2, 3, and 4. An inlet tube 5 which receives the uid from the device or tool exhaust (not shown) extends within expansion chamber 2, and is provided with a series of peripheral openings 6 which permit the fluid to pass from within tube 5 to expansion chamber Z. A closure 7 is provided on the end of tube 5. A conical detlector 8 attached along its outer lip to or engaging against the inner wall of sleeve 1 may be integral with or securely attached to the inlet tube 9 within expansion chamber 3. Tube 9 is also provided with an end closure 10 and peripheral perforations 11 permitting passage of fluid from within tube 9 into expansion chamber 3. Each successive expansion chamber is provided with a conical deilector 8 attached to or part of an inlet tube 9 having end closure 10 and peripheral perforations 11, but the total area of openings 11 increases in successive expansion chambers to provide for the expanded fluid. An exhaust 12 is provided from the final expansion chamber and should have an exit volume at least equal to the inlet capacity of inlet tube 5.

The cross-section of the silencer may take any form desired but desirably is circular as shown in the drawing and similarly the tubes 6 and 9 will be of similar configu ration to that of the cross-section of sleeve l so that tubes 6 and 9 are desirably circular in section and sleeve 1 is circular, but may be square in section when sleeve 1 is square in section, oval in section when sleeve 1 isoval in section, etc. So too a conical deilector 8 is desirably used with a circular sleeve and inlet tube but may have any other coniiguration. Each of the tubes 6 and 9 may be further supported by straps 13 is desired, or in any other way.

Desirably the expansion chambers successively increase in volume which is readily effected by increasing the diameters successively of such chambers or in any other way.

The inner wall of sleeve 1 is desirably lined throughout its length with sound absorbing material 14. A most desirable type of sound absorbing material is illustrated in Figure 3 of the drawing. As there shown, a layer 15 of non-metallic material such as rubber, plastic, etc., having a backing 16 such as of felt cemented to layer 15, is provided with a. cellulate structure. For that purpose layer 1S has a multiplicity of cells 17 each having an opening 18 to the outer surface of layer 15. Desirably in a number of said cells 17, and desirably in all of them, a freely-moving non-metallic ball 19 of rubber, plastic, foam rubber, Bakelite, etc. is placed to aid in dissipation of the energy of the pneumatic uid. To illustrate further such sound absorbing material and a manner of making it, reference is made to Figures 4 to 7.

A layer 15 of rubber, plastic, or any other desired nonmetallic material may be produced as by casting or molding to provide a multiplicity of cells 17 therein throughout the layer. The cells 17 are desirably parti-spherical with a truncated portion 2t) open to one face of layer 15. Such cellulate structure may be readily produced by casting etc. in the form shown; and due to the flexibility of the material, readily removed from the mold. Each cell 17 is drilled through to produce an opening 21 thereinto, such opening 21 exposing the interior of the cell to the pneumatic tluid. Each opening 21 is desirably countersunk as at 22 but the openings 21 should have a crosssectional diameter less than the ball 19 to be placed therein. The desired ball 19 is inserted into each cell 17 through truncated portion 20, and backing 16 then secured to the layer 15 to seal balls 19 within cells 17. The sealing operation may be by hot bonding, by cement, or otherwise depending on the nature of the material, by backing 16 and layer 15. Backing 16 may be of the same or different material from that of layer 15 but is desirably non-metallic. The resulting sound absorbing structure is then positioned within the expansion chambers or otherwise utilized. The balls freely movable within the cells are particularly effective for dissipation of the energy of the pneumatic tluid while silencing the operation.

As stated above, nonetallic balls are desirably used in the cells to assist in the sound dissipation. In those cases, such as in the large, giant or jumbo size pavement busters where the sound dissipating chambers are sutliciently large, and the rush of uid sufficiently great in pounds pressure, a light metallic ball like a light Weight metallic ball bearing may be used. But in smaller hand tools as used for example by women in riveting, for instance, aeronautical skin covering, a light plastic, e. g. Bakelite, ball should be used, as in any case where otherwise the ball would lie dormant in the cell.

Having thus set forth my invention, I claim:

1. ln a silencer for pneumatic actuated devices, a plurality of expansion chambers successively connected, and a sound absorbing structure in each of said expansion chambers, said structure including a cellulate Wall of nonmctallic material the cells being open to the expansion chamber, and a freely movable non-metallic ball in a number of said cells.

2. In a silencer for pneumatic actuated devices, an eX- pansion chamber and a sound absorbing structure in said expansion chamber, said structure including a cellulate :it non-metallic material, the cells being open to the expansion chamber, and a freely movable non-metallic ball in a number of said cells.

3. A silencer as in claim 1, in which the expansion chambers are positioned lineally Within an elongated sleeve which chambers successively increase in diameter, an inlet tube Within each chamber to receive pneumatic fluid, each tube having peripheral openings to pass the fluid from within the tube to the expansion chamber, a conical deector between successive expansion chambers to deiiect the fluid from a preceding expansion chamber to the inlet tube of a succeeding expansion chamber, and an exit pipe for fluid from the last expansion chamber.

4. A silencer as in claim 3 in which the sound absorbing structure lines the internal Wall of the sleeve.

5. A silencer as in claim 4 in Which the peripheral openings increase in total area in successive expansion chambers.

6. A silencer as in claim 5 in which the fluid exit has a cross-sectional area at least as large as that of the first inlet tube.

7. A silencer as in claim 2 in which the expansion chamber is enclosed Within a sleeve, an inlet tube is positioned Within the chamber to receive pneumatic fluid, the tube having peripheral openings to pass tiuid from Within the tube to the expansion chamber, and an eXit pipe for fluid from said expansion chamber.

8. A silencer as in claim 7 in which the sound absorbing structure lines the internal Wall of the sleeve.

9. A silencer as in claim 8 in which the fluid exit has a cross-sectional area at least as large as that of the inlet tube.

10` In a silencer for pneumatic actuated devices, an elongated sleeve, a plurality of expansion chambers successively connected lineally Within said elongated sleeve which chambers successively increase in diameter, a sound absorbing structure on the internal Wall of said sleeve, said sound absorbing structure including a cellulate wall of non-metallic material, the cells being open to the expansion chambers, an inlet tube within each chamber to receive pneumatic fluid, each tube having peripheral openings to pass the fluid from Within the tube to the expansion chamber, a conical deflector between successive expansion chambers to deflect fluid from a preceding expansion chamber to the inlet tube of a succeeding expansion chamber, and an exit pipe for fluid from the last expansion chamber.

11. A silencer as in claim 10 in which the peripheral openings increase in total area in successive expansion chambers.

12. A silencer as in claim 11 in Which the fluid exit has a cross-sectional area at least as large as that of the first inlet tube.

References Cited in the ile of this patent UNITED STATES PATENTS 532,374 Hermes Jan. 8, 1895 618,479 Pennington Jan. 31, 1899 1,766,945 Riehm June 24, 1930 1,937,889 Howard Dec. 5, 1933 2,152,205 Morrison Mar. 28, 1939 2,392,559 Varma Jan. 8, 1946 2,562,101 Hoyle July 24, 1951 2,600,236 Gibel June 10, 1952 FOREIGN PATENTS 251,210 Great Britain Apr. 29, 1926 753,605 France Oct. 20, 1933 845,582 Germany Aug. 4, 1952 

